Orthomobility VGK125P User manual

rthomobilit
naturally adaptive
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Instructions Manual

2Form IFU001r07 Orthomobility Ltd
Contents
1. α-logic Control
1.1. Intended Purpose
1.2. Recommended User Profile
1.3. Normal Use
1.4. Non-Ordinary Use
1.5. Expectation Management
1.6. Extreme Device Settings
1.7. Extreme Temperatures
1.8. Prevention Of Overheating
1.9. Compatibility
1.10. Body Weight
1.11. Wear And Tear
1.12. Dirt And Water
1.13. Stairs
1.14. Storage
2. Alignment
2.1. Socket Flexion
2.2. Foot Alignment
2.3. Swing Deviations
2.4. Kneeling
3. Controls
3.1. Swing Release Dial
3.2. Stance Mode Selector
3.3. Stair Mode
3.4. Ultra High Resistance
3.5. Cycling Mode
3.6. Swing Phase
3.7. Terminal Impact Dampening
4. Warranty
5. Care And Maintenance
6. Liability
7. Training And Education
8. Declaration Of Conformity
9. Ordering Numbers

3
1. α-logic Control
The technology means to adjust the valve settings in
accordance to user demand, i.e. to regulate the power
that produces the desired motion and functionality,
continuously manages flow and force levels inside
the joint using intuitive, α-logic control. This Motion
Feedback System (MFS) includes the Vortex Metering
System (VMS), the patented flow control technology
that counteracts possible variations in body weight and
operating temperature.
1.1. Intended Purpose
The VGK is intended to be used solely in lower extremity
prosthetic limbs as a prosthetic knee joint.
1.2. Recommended User Profile
The VGK joint is recommended for independent
prosthetic users, typically of mobility classes K2, K3,
K4. The patient weight can be up to 125 Kg. Users with
significant comorbidity must be carefully monitored in
the rehabilitation period to ascertain the suitability of the
device for their needs.
1.3. Normal Use
The VGK has been developed for ordinary mobility use:
walking, sitting, kneeling, cycling and occasional wetting
by rain or tap water.
1.4. Non-ordinary And Extreme Use
Non-ordinary and extreme use may from time to time be
required and known prior to the occasion. Such use may involve
water and dirt, or shock and forceful use. Whereas these may
be considered as part of intended use, it will be required that
written permission is sought from the manufacturer so that
such non-ordinary use can be risk assessed, supported, or on
grounds of risk be denied. A considered permission/denial/
support program will be discussed on request.
Fig 1: Adaptive α-logic Control Hydraulic Knee.
1
24
3
5
1Heel rise limiter / knee flexion limiter
2Yield valve with scale
3Stance mode selector
4Swing control for tall people
5Swing release dial
6Cycle mode with safety catch
7Ultra high resistance mode
8Yield mode
6
7
8

4Form IFU001r07 Orthomobility Ltd
1.5. Expectation Management
Advise your patient that this device, whereas designed
to offer a service compatible with a high level of safety,
the same high level of safety is liable to increase their
expectations of their ability, and consequently your patient
may ultimately find limits of performance of the device.
When such an event happens, they are asked to remember
the circumstances and report any event back to their CPO.
1.6. Extreme Device Settings
Whereas the VGK permits a high level of resistance in yield,
this function is not intended to effectively lock the joint
at certain knee angles over 30 degrees when significant
weight is placed upon the leg: the hydraulic pressures
could damage the device. This warning does not apply to
ordinary ‘leg over leg’ use.
1.7. Extreme Temperatures
The VGK has been designed for a stable performance over
a range of temperatures, the use in very low temperatures
(sub zero) may cause some stiffening in the yield action of
the joint, which in hands-free slope and stairs descent could
cause an imbalance. In such a case it is advised to first try
to walk down close to a handrail. In elevated temperatures
(40 degrees plus) the VGK maintains its performance fairly
well.
1.8. Prevention Of Overheating
Prolonged walking down slope and downstairs will heat
up the joint due to energy dissipation. The frame acts as
a cooling fin, and using an open structure cosmesis will
optimise the temperature of the VGK.
1.9. Compatibility
The VGK has been designed to be compatible with the full
complement of prosthetic components such as energy-storing
feet, hydraulic ankles, hip components, shock absorbers, etc.
1.10. Body Weight And Additional Load
The VGK has been designed to allow for patient body weight of
up to 125 Kg and these persons, at this maximum body weight,
to carry not more than 15 kg of additional load on a daily basis.
1.11. Wear And Tear
As with any mechanical device, mechanical wear and tear will
eventually occur, and the user and CPO are required to see
that regular inspections and maintenance are carried out.
1.12. Dirt And Water
In the event of ingress of water and dirt, the VGK can be
washed with water and if so required, with soap. Contact with
salt water requires cleaning with tap water. It is important to
make sure that no sand or stones are trapped between moving
parts, as this may lead to system damage. In case of use in
environments with loose particles, the use of a protective
(fabric) cover is recommended.
1.13. Stairs
The use of handrails or banisters is recommended when
descending downstairs.
1.14. Storage
The VGK must be stored in an extended position.

5
Fig 2: A vertical Hip-Knee-Ankle line is the preferred alignment.
A posteriorly placed hip/greater trochanter is liable to make
swing release more difficult.
2. Alignment
The alignment of the VGK follows the ideal of a straight
hip-knee-ankle line. If the residual limb requires socket
flexion, the hip-knee-ankle line should be maintained
as well as possible. The distal pyramid must be used for
neutral axial alignment only if body weight exceeds 100kg.
2.1. Socket Flexion
Socket flexion produced from tilting the socket at the distal
socket only results in the knee centre to be anterior to the
hip-ankle line. This may result in a diminished or absent
knee extension moment in late stance, and may make swing
initiation difficult. Fig 2 illustrates the preferred set up,
irrespective of any hip flexion accommodation.
2.2. Foot Alignment
The VGK requires a toe load in late stance to release into
swing. Too much dorsiflexion may cause insufficient
forefoot loading and difficulty in releasing the knee into
swing. Equally, an unusual high heel on the shoe would
cause difficulty in swing initiation.
2.3. Swing Deviations
It must be borne in mind that the mass of the knee device
helps the bilateral balance of body mass, but requires a
correct mediolateral placement for optimum performance.
As a possible guide for bench alignment, the VGK should be
located in the plane of action as defined by the biological
ball and socket hip joint and the push-point of the distal end
of femur. In shorter residual limbs more lateral placement
of the VGK is expected.
1
2
3
1Hip 2Knee 3Ankle joint

6Form IFU001r07 Orthomobility Ltd
2.4. Kneeling
Extreme or maximum knee flexion will cause the socket to
touch the hydraulic unit. This unit can take the forces of
kneeling and squatting provided the contact is made in the
region as indicated in fig 3. It is important to measure the
indicated contact point to be 100 +/- 5 mm from the knee
axis. If required, the socket may need a local build up, so
that the internal structure of the hydraulic takes the load at
the correct point. DO adhere to this rule. Alternatively, the
socket may rest on the hydraulic valve housing.
3. The Controls
3.1. Swing Release Dial
The VGK relies on the presence of knee extension and toe-
load for swing phase release. This condition is natural in
terminal stance. For most users this switching behaviour is
set to be as light as possible. For bilateral amputees the
transition may need to be more deliberate also to secure
standing balance. If the threshold for switching to swing
mode must be increased, the swing release dial as in fig 4
must be turned clockwise. This increases the pre-load
on the PolyUrethane spring, requiring more weight on
the forefoot before the PolyUrethane Spring gets further
compressed due to the swiveling action of the distal knee
(or spring housing), which supports swing release. When
used outside the parallel bars, no slack rocking action may
be present between the frame and the distal knee.
Fig 3: Kneeling onto the cylinder is permissible when
the contact point is +-100mm from the axis.
Fig 4: Swing release dial.
1
2
1
2
3
1Kneeling socket touch point must be +-100mm
2The socket cannot support on the cylinder section
3Alternative socket touch point
1Easier to release 2Safer

7
1
2
3
4
5
6
7
1Indicator
2Swing release dial for tall people
3Safety catch sensitivity
4Stance mode selector
5Ultra high resistance mode
6Cycle mode with safety catch
7Yield mode for slope and stair descent
It is important for the patient to understand WHAT NOT
TO DO & AVOID
Forceful hyperextension as in hitting the ground hard
with forceful extension immediately followed by a knee
flexion moment may bring the knee into swing mode with
consequential loss of weight bearing capacity. An example
of such non-recommended use is attempting to land hard
on the mid-foot onto a curb or step and rock over the
foot up onto the curb or step. Remember that the joint
will release into swing mode when the knee centre is in a
state of hyper extension and simultaneously the mid and
forefoot is loaded, followed by a knee flexion moment.
This user induced fail-mode is unlikely to happen in
ordinary walking and fast walking style, but can happen in
exceptional circumstances. Confidence in the VGK should
not be lost if the usual safe behaviour continues after any
such incident of exceptional use.
3.2. The Stance Mode Selector
The stance mode selector allows the choice of stance
mode: the normal stairs mode with yielding, the ultra high
resistance mode, and the free cycling mode with Safety
Catch.
3.3. Stairs Mode
The ‘yield’ function refers to the joint flexion behaviour
under load of body weight such as occurs in downstairs
walking. The factory default setting provides too much
resistance to the experienced user, yet provides a safe
resistance for the first time user. The yield is adjusted
as per fig 5. A clockwise turn of one dot provides a stepped
increase in yield resistance, and vice versa. To get the right
setting for the user, allow them to descend down from the last
step of a stair and adjust until comfortable. Adjust as required
when more steps are taken in sequence.
Fig 5: Dynamic Adjustments.
1 2
1Do Not 2Avoid

8Form IFU001r07 Orthomobility Ltd
3.4. Ultra High Resistance Mode
Ultra high resistance mode, for ease of reference indicated
by a ‘padlock’ is an ultra high resistance mode effectively
blocking the yielding, but allowing free swing as long as
the walking speed is not too high. For this reason this
mode is NOT A FULL LOCK. The ultra high resistance
mode is activated by placing the lever in the mid position.
3.5. Cycling Mode
For longer cycle rides the Stance mode selector may be
toggled to Cycle. See fig 5. This renders the VGK free as
long as the knee angle speed does not exceed the pre-set
safety value. When the manual Stance mode selector is not
set back to Stair or Lock mode, a safety valve will aid in
reducing risk of collapse after use of the bicycle. A feeling
of uncomfortable slackness in the joint in this use mode
is normal, and the user is reminded to switch the stance
mode selector to the normal stair mode. The cycling mode
allows free movement of the knee within the limits of a
pre-set flexion rate.
Setting Cycling speed: The factory setting of the cycling
function is on ultra-safe! In this factory setting the cycling
function may not work for the user. To get started, put the
Cycle stance mode selector switch to Stair mode. In the
centre of the The stance mode selector switch there is a
small safety screw, the Safety Catch sensitivity (see fig 5)
that sets the permissible rate of knee flexion before the
safety valve is activated.
3.5.1. Setting Cycling Speed
To explore this mode, first test-bend the prosthesis in the stair
mode: it does not bend easy. Put the The stance mode selector
switch to Cycle mode, test the knee, it does not bend easy at
a fast rate. Put the cycle switch to Stair mode, turn the Safety
Catch in fully. Put the cycle switch to Cycle, test the knee, it
bends very easy. Bend the knee fast, it still bends easy. Wind
the Safety Catch anticlockwise for two full turns, test the knee
in bending slowly and fast. If no difference, repeat procedure.
A setting will be found where slow movement is easy, and fast
movement is prevented after a little slack movement. This is
the basis for the VGK to differentiate between the slow cycling
movement that is to be permitted, and the fast movement that
may occur in an otherwise uncontrolled collapse of the joint if
it were left in the Cycle mode.
3.5.2. Adjustment with user
For clinical set-up, put the Stance mode selector to Stair mode,
turn the Safety Catch sensitivity fully in. The user cycles, and
incrementally the Safety Catch sensitivity is turned anti-
clockwise until the safety feature applies itself during cycling.
Agree with the user how much less sensitive they need the
safety feature to remain safe in walking if they attempt a
simulated collapse. Naturally, the faster cycling is required,
the less safety is available in walking!
NOTE: If the cycling function is not required, make sure the Safety
Catch sensitivity is turned fully anticlockwise, the factory setting.
This minimises any free knee movement if the patient touches the
selector switch.

9
3.6. Swing Phase
The swing phase is controlled by the Heel Rise slider (see
also figs 1 and 6), and the Swing button (see also fig 5). The
swing phase resistance is divided in two parts. From 0 to 40
degrees (approx.), the Swing dial gives more resistance to
this initial swing phase, and is used with only TALL People
as per fig 5. (When shank length causes long pendulum
effect). Clockwise turning increases the resistance,
and vice versa. Normally the swing button is set to light
resistance to minimise the work necessary by the user (i.e
as fully open as possible). The MAIN control is the Heel
Rise Slider. Heel rise control, (or Maximum Knee flexion),
is achieved by setting the lever as indicated in figs 6 & 7.
A leftward swivelling movement lowers the maximum heel
rise / maximum knee flexion and increases the ‘power’ of
the knee joint to push the foot forward. A rightward move
increases the maximum heel rise and lowers the ‘power’
delivered to the foot.
3.7. Terminal Impact Dampening
The terminal impact dampening is auto-corrective and
dynamically adjusts itself to the walking speed, and is not
otherwise adjustable.
NOTE: there is no external adjustment to alter the extension
resistance.
4. Warranty
Orthomobility Ltd. offers a limited two year warranty against
defects in materials and workmanship in accordance with
terms and conditions of sale. Defects arising from non-
ordinary and extreme use, and fair wear and tear are subject
to the manufacturer’s discretion. REGULAR / PLANNED WET
ENVIRONMENT USE requires manufacturer’s AGREEMENT.
Fig 7: Heel Rise Slider.
Fig 6: Adjustment for dynamic swing phase.
1
1 2
1Selectable range of heel rise control (Heel rise slider)
1Less heel rise 2More heel rise

10 Form IFU001r07 Orthomobility Ltd
Building Height In Sitting
Building Height Below Knee
Building Height Above Knee
5. Care And Maintenance
Due to fair wear and tear, the solid bearings may show wear
and may need replacing from time to time. Please refer to
www.orthomobility.com for more specific maintenance
instructions.
6. Liability
As the use of a prosthetic device includes a necessary risk,
the manufacturer limits the liability arising from the use of
the VGK to that liability directly arising from a malfunction
of the device due to faulty materials and/or workmanship
and exclude any other special, incidental or consequential
damages. For full details see Terms and Conditions on
invoice.
7. Training and Education
Orthomobility Ltd. continuously add new material of shared
experience on their website, and clinicians are expected
to check for new information to ensure continuous best
practice with VGK.
TOPICS OF EDUCATIONAL INTEREST ARE:
»The Luetkemeyer-technique of walking downstairs.
»Dealing with very soft ground when walking down
slope (like thick mulch).
»Training primary amputees.
»Case studies with double and triple amputees.
»Use in the great outdoors: successes and challenges.
Product Serial
Number
mm
mm
mm

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8. Declaration of Conformity
The VGK and its variations made by Orthomobility Ltd,
Reg 5143375 conform to the MDD Directive 2007/47/EC and
93/42/EEC and ISO 10328:2006
9. Ordering Numbers
VGK125P VGK Knee joint 125kg, with standard pyramid
VGK125A VGK Knee joint 125kg, with TK Anchor adapter
VGK125M VGK Knee joint 125kg, with M36 threaded head
Add Suffix ‘H’ to partnumber if used for Hip Disarticulation.
e.g; VGK125MH, VGK125PH
Add Suffix ‘O’ to partnumber if used for Osseo Integration.
e.g; VGK125MO, VGK125PO
For extended information visit: www.orthomobility.com

Websites:
www.lothfabenim.nl
www.orthomobility.com